Conventional devices that are used for cleaning the interiors of soiled chimneys usually only effectively remove the soot but leave the majority of the tar and creosote in the chimney. Tar and creosote buildup in the chimney is dangerous because it causes a potential fire hazard. Both tar and creosote are inflammable at high temperatures.
A number of devices and apparatus have been invented in the past for the purpose of cleaning the interiors of soiled chimneys. The following patents disclose apparatus that are purportedly useful for cleaning chimneys.
______________________________________ U.S. Pat. No. U.S. Pat. No. ______________________________________ 195,445 2,455,001 1,230,310 4,090,271 1,392,202 4,333,200 1,582,309 4,490,879 1,615,733 4,492,000 ______________________________________
Five of the located patents disclose chimney scrapers that have no ability to exert a force against the wall of the chimney. Specifically, they do not contain any spring device to maintain the scraper blade against the chimney wall. These patents are U.S. Pat. Nos. 195,445; 2,455,001; 4,090,271; and 4,490,879.
Five other U.S. patents, namely U.S. Pat. Nos. 1,392,202, 1,582,309, 1,615,733, 4,333,200 and 4,492,000, disclose chimney scrapers containing springs but they do not contain any mechanism to adjust the lateral force applied by the spring. Two of the patents, U.S. Pat. Nos. 4,492,000 and 1,392,202, use the contraction force of a spring to apply a lateral force. U.S. Pat. Nos. 1,582,309 and 1,615,733 use spring expansion force for this purpose. These devices do not maintain the blade at an angle optimum for cleaning difficult creosote.
Most of the above patents (except U.S. Pat. No. 1,230,310 and 2,445,001) disclose two blades, one on either side of the scraper, for cleaning opposite sides of the chimney simultaneously.
U.S. Pat. No. 1,230,310 issued June 19, 1917 to S. T. MacDonald for a chimney cleaner. MacDonald discloses means for applying a lateral force to a single scraper blade through the use of an adjustable spring mechanism. The blades do not maintain the optimum creosote cleaning angle.
MacDonald appears to use rotational torsion force exerted by a spring when it is twisted, rather than longitudinal deformation to apply the force. The adjustment mechanism in MacDonald does not directly adjust the rotational torsion force exerted by the spring MacDonald adjusts the moment that the spring applies to the pressure arm by varying the distance between the spring pivot point and the pressure arm pivot point.